In a wireless communications system, a transmit end and a receive end acquire higher rates by using multiple antennas by means of spatial multiplexing. Compared with general spatial multiplexing methods, an enhanced technology is that the receive end feeds back channel information to the transmit end, and the transmit end uses some transmission precoding technologies according to the obtained channel information, which greatly improves transmission performance.
In a Long Term Evolution (LTE) system, to implement effective control and scheduling of different user equipments (UE) for a base station, the UEs need to feed back some channel state information (CSI) to the base station by using an uplink channel, where this channel state information may include a channel quality indicator (CQI), a precoding matrix indicator (PMI), and a rank indicator (RI).
In 3rd Generation Partnership Project release-12 (3GPP Rel-12) of LTE, an antenna scale is extended from a horizontal linear array into a horizontal-vertical two-dimensional planar array (that is, a common active antenna system (AAS)), and a quantity of antennas also further increases from a maximum quantity of 8 in 3GPP Rel-11 to 16, 32, and 64. As the antenna scale increases, complexity of corresponding CSI measurement and feedback also correspondingly increases, and there is no specific technical solutions applicable to the foregoing large-scale planar antenna array in the prior art. If only a method for CSI measurement and feedback in 3GPP Rel-11 is simply extended, measurement and feedback overheads are heavy, and a waste of uplink channel resources is caused.